At a time when the Supreme Court seems closer than ever before to treating sexual orientation as a suspect classification, consideration of the legal definition of sexual orientation is both timely and important. The Court’s 2015 decision in Obergefell recognizes two guideposts for defining sexual orientation: its immutability and normalcy. While other scholars offer rich and nuanced accounts of the fight for gay, lesbian, transgender, and bisexual rights, they do not fully analyze the history of sexual orientation as a legal category. This Article closes that gap, illuminating the hidden costs of the definition of sexual orientation that Obergefell endorses.

In the past, definitions of sexual orientation based on immutability helped courts turn away equal protection arguments because of the “real” biological differences between same-sex and opposite sex couples. In the context of sexual orientation, arguments based on immutability admit the possibility that other “real” differences will undermine an otherwise promising equal protection claim, particularly with respect to reproduction.

Immutability-based definitions also raise the possibility of discrimination on the basis of conduct. The conduct-status distinction has cropped up as courts weigh conscience-based objections to otherwise applicable civil rights protections for gays and lesbians. While conscience claims resting on the conduct-status distinction have failed so far, the history of sexual orientation as a legal category, together with Supreme Court jurisprudence on the subject, offers reason for concern. The Supreme Court has been less willing to equate conduct and status when discriminators invoke what the courts describe as a legitimate moral or religious objection to a particular act, like abortion. In describing homosexuality as an immutable sexual orientation rather than partly as a legitimate choice, the Obergefell Court assumes the validity of moral objections to both same-sex marriage and homosexuality. Immutability arguments do not address whether individuals’ choices deserve respect or tolerance, making it harder to argue against conscience-based objections. In the aftermath of the Court’s Obergefell decision, it will be just as important to promote a proper understanding of sexual orientation as it will to expand antidiscrimination protections.